The men – four Croats and a Serb – were arrested in Croatia following an 11 month-long investigation by police in Italy and their counterparts in Zagreb.

In one of the most audacious heists Italy has witnessed in recent years, thieves stole a pendant brooch and a pair of earrings worth an estimated £2.3 million from the exhibition in the Doge’s Palace in St Mark’s Square in January.

The jewellery was from the famed Al Thani Collection, owned by Qatar's Sheikh Hamad bin Abdullah Al Thani and normally kept in London.

The diamond earrings that were stolen from the collection on display in the Doge's Palace in VeniceCredit:
Al Thani Collection/AP

The gang struck on the last day of the four-month exhibition, which featured exquisite jewellery and precious stones spanning four centuries from the Mughal Empire to the present.

Despite being caught on security cameras, the thieves managed to deactivate an alarm system and force open a reinforced display case before disappearing into crowds of tourists and escaping.

Police said the leader of the gang is believed to be a member of the Pink Panther syndicate, which is accused of carrying out dozens of well-planned, high-profile jewellery heists across Europe and Asia.

He is wanted in connection with a seven million euro diamond robbery in Basel, Switzerland, in 2011.

The Pink Panther gang has become well-known for executing lightning-fast, high value robberies.

In past raids, gang members have worn wigs to disguise their identities and threatened staff with firearms, before smashing open display cases with pickaxes and hammers.

The pendant brooch that was stolen by the gang, who targeted the Doge's Palace in January Credit:
Al Thani Collection/AP

They were nicknamed the Pink Panthers after British detectives raided a house in London and found a $750,000 diamond ring hidden in a pot of face cream – a ruse used in one of the classic Peter Sellers comedies.

Members mostly come from Serbia, Montenegro, Bosnia and Croatia, authorities say, with many suspected to be highly-trained veterans of the Balkan wars.

They have made hundreds of millions of pounds by targeting upmarket watch and jewellery stores across the world.

During one heist in St Tropez, they ran down to the harbour and made off in a speed boat.

Italian authorities did not disclose whether the jewels stolen from Venice had been recovered.

But Italian police did reveal on Friday that the gang had made two previous attempts to steal jewels from the collection – once on December 3 last year and again on January 2. They were either disturbed or had difficulties forcing open the display cases.

The jewels were stolen from an exhibition called Treasures of the Mughals and the Maharajahs in VeniceCredit:
Andrea Merola/Ansa

The pendant brooch, featuring a flawless 10-carat diamond surrounded by diamonds and rubies, was worth more than $2 million, while the pear-shaped diamond earrings were worth $1 million.

The items were designed by Bhagat Jewelers, an exclusive Mumbai jeweler, in 2011 and 2014.

Prior to coming to Venice, the collection, "Treasures of the Mughals and the Maharajas", had also been on display in Paris, New York, Japan and in London's Victoria and Albert Museum.

The arrests were welcomed by Luigi Brugnaro, the mayor of Venice, who said the city had offered “maximum collaboration” to investigators.

The operation to find the alleged thieves had been “complex” because it was based on collaboration between the Italian police and their counterparts from several countries, the mayor said.